Photons are easily created and destroyed. Unlike matter, all sorts of things can make or destroy photons. Similarly, when a photon of the right wavelength strikes an atom, it disappears and imparts all its energy to kicking the electron into a new energy level.

They can have a positive (+) or negative (−) electric charge. Up, charm, and top quarks have a positive 2/3 charge. Down, strange, and bottom quarks have a negative 1/3 charge. So protons are positive because there are two ups and one down quark, giving a net positive charge: ((+2/3) + (+2/3) + (-1/3) = +3/3 or +1) .

For all we know, yes. All composite particles and free elementary particles* can only have integer charge. Thus far, all charges of free particles is -1, 0, +1 or +2. Thus, there is no possible mixture of quarks that both conserves Color Confinement and has fractional electromagnetic charge.

Therefore, one atom is 1.00055469×10^30 times larger than a photon, thus we can say atom made by 1.00055469×10^30 photons. Similarly, all matter made by photons. Again, one photon contain 10^107 unknown particles.

They’re real. We can make electrons (and positrons) out of photons in pair production. And you are made out of electrons and other particles that are equally real. Photons exist and best described as packets of energy or particles.

However, two photons heading towards each other can indeed collide indirectly. A photon can spontaneously degenerate into a particle with mass and its antiparticle in a process known as pair production. In this process, the energy of the photon is completely transformed into the mass of the two particles.

one billion billion years

Light is made up of particles called photons that travel like waves. Unlike some types of particles, they do not decay, meaning that they do not spontaneously turn into other types of particles. With nothing to stop them and no chance of decaying, the will keep going forever.

The speed of light is normally about 186,000 miles per second, or fast enough to go around the world seven times in the wink of eye. Scientists succeeded in slowing it down to 38 mph. They did this by shooting a laser through extremely cold sodium atoms, which worked like “optical molasses” to slow the light down.

Light dissipating The fact that we can see the Sun and stars shows that light can travel over enormous distances (150 million kilometres from the Sun). In fact there is no known limit to how far light can travel.

Sound requires a material medium in which to propagate. It cannot travel forever because the material in which it propagates does not go on forever.

Light travels forever until it is absorbed. However, if it travels a very long way indeed, it is redshifted by the expansion of the universe.

We know light can travel through a vacuum because sunlight has to race through the vacuum of space to reach us on Earth. Sound, however, cannot travel through a vacuum: it always has to have something to travel through (known as a medium), such as air, water, glass, or metal.